IPM motors or machines generally include a stator with excitation windings and a rotor having embedded magnets, e.g., an interior permanent magnet rotor. These rotors allow permanent magnet synchronous motors to operate with constant power over a wide range of speeds. The magnitude of this range of speeds, i.e. the ratio of the maximum speed to the minimum over which the constant power is maintained depends on the ratio of the inductances along the two orthogonal axes—one in the direction of the magnet flux referred to as the d axis and the other 90 electrical degrees from the d-axis, called the q-axis.
In designing such motors, various factors need to be addressed including among other things mechanical stress during operation, flux leakage and/or cogging torque.